This invention relates to archery bows and more particularly to a draw length indicator for indicating the proper bow tension for arrow release.
For consistent accuracy of performance in the sport of archery, it is generally necessary to draw the arrow and bow string back to a certain predetermined point prior to release of the arrow. The distance through which the tail of the arrow is drawn is generally referred to as the draw length. This draw length is a variable which changes with different archery participants and is a function of their body dimensions, particularly their arm length. In order to assure consistency in the force exerted in drawing the bow, it is desirable to have some indications that the tip of the arrow is properly positioned with respect to the shank portion of the bow. This determination is difficult for the archer to make since his attention is typically being employed to aim the device and direct sighting of the tip of the arrow can be difficult.
Other individuals skilled in the archery art have realized the desirability of employing a draw length indicator. For example, in U.S. Pat. No. 3,450,122, issued June 17, 1969 to Clyde Diamond there is apparently disclosed a bow and arrow mechanism utilizing a magnet carried by a central portion of the bow which magnetically energizes a tip end of the arrow which in turn energizes and closes a switch when the arrow and its head have been drawn back to a proper shooting position. However, the device illustrated in the Diamond patent possesses several significant disadvantages. In particular, a significant amount of the activity undertaken by archery enthusiasts involves the sport of hunting using the bow and arrow with what is known as a broadhead tip. Such a tip is more particularly illustrated in FIG. 3 which is described and discussed below. In the device illustrated in the aforementioned patent, an energizing magnet is disposed in the shank of the bow itself and does not permit the use of arrows possessing broadhead, or hunting, tips. The Diamond device does not work with these hunting arrows because these broadhead tips do not clear the body of the bow and fail to reach the energizing magnet. Furthermore, the use of the device in the Diamond patent requires that the bow be bored to allow for insertion of batteries. Furthermore, the required boring must be done at the highly stressed midportion of the bow limb. Additionally, the device disclosed in the Diamond patent is inoperable for newer type bows. Lastly, this device requires special fitting and adaptation to each bow.
Another draw length indicating device is apparently disclosed in U.S. Pat. No. 4,179,613 issued Dec. 18, 1979, to James T. Koren. This device depends upon a photoelectric detector to sense when the head of the arrow has passed to provide an indicating signal that the draw length is proper. However, this device also possesses significant disadvantages, particularly for the hunting archer. Specifically, the use of a photocell necessarily makes the sensor's sensitivity dependent upon ambient light conditions. While the Koren device appears to be able to adjust its sensitivity, nonetheless light conditions can change rapidly particularly at the hours of dawn and dusk. Such sensitivity adjustments can be a significant distraction to the hunter. Furthermore, and even more importantly, the device in the patent to Koren is also inoperable when a broadhead tipped arrow is employed. Such an arrow will simply not clear the detector in front of the bow shank to provide the necessary indicating signal in the Koren apparatus. Additionally, the apparatus of Koren employs a mercury switch for insuring horizontal bow operation. However, much successful hunting is accomplished from tree stands or similar cover in which the bow cannot be maintained in a horizontal position. Accordingly, the draw length indicating device in the Koren patent is not effective for use on bows where the intended function is that of hunting.
There is also apparently disclosed an archery release indicating assembly for use with an archery bow in U.S. Pat. No. 3,866,592 issued Feb. 18, 1975 to Richard F. Carella. The device in this patent employs a mechanical bracket, spring and trip device for providing an audible sound, indicating to the archer that the arrow should be released. However, it should be noted that audible signals are generally undesirable in hunting situations. A similar audible signalling device for a draw length indicator is also apparently shown in U.S. Pat. No. 3,499,414 issued Mar. 10, 1970 to Arthur J. Frydenlund. Again, the disadvantages of an audible signal are noted. Another audible signal producing device is apparently shown in U.S. Pat. No. 3,669,059 issued June 13, 1972 to Frank T. Stuart. In this device, an audible "clacker" includes two metal strips of aluminum and a spring element sandwiched between the metal strips together with an adhesive member that is used to attach the member to the bow. The spring element appears to be biased outward from the bow by an arrow during the drawing of the bow but when the spring element moves out of engagement with the arrow, the spring element slaps the bow and produces the audible signal to indicate that the arrow has been drawn the proper distance. Lastly, there is apparently provided in U.S. Pat. No. 4,183,346 issued Jan. 15, 1980 to Fernando V. Trancosso, Jr., a device for providing an adjustable draw check or stop to indicate draw length. However, it appears that in addition to being significantly different from the present invention, that it also has the signal disadvantage of interference with the arrow's fletchering.
Accordingly, draw length indicators previously employed by those in the archery arts have not properly addressed the problems of the archery enthusiast who is also a hunting aficionado.